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denoland-deno/cli/js/buffer.ts

213 lines
5.5 KiB
TypeScript

// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
// This code has been ported almost directly from Go's src/bytes/buffer.go
// Copyright 2009 The Go Authors. All rights reserved. BSD license.
// https://github.com/golang/go/blob/master/LICENSE
import { Reader, Writer, ReaderSync, WriterSync } from "./io.ts";
import { assert } from "./util.ts";
// MIN_READ is the minimum ArrayBuffer size passed to a read call by
// buffer.ReadFrom. As long as the Buffer has at least MIN_READ bytes beyond
// what is required to hold the contents of r, readFrom() will not grow the
// underlying buffer.
const MIN_READ = 512;
const MAX_SIZE = 2 ** 32 - 2;
// `off` is the offset into `dst` where it will at which to begin writing values
// from `src`.
// Returns the number of bytes copied.
function copyBytes(src: Uint8Array, dst: Uint8Array, off = 0): number {
const r = dst.byteLength - off;
if (src.byteLength > r) {
src = src.subarray(0, r);
}
dst.set(src, off);
return src.byteLength;
}
export class Buffer implements Reader, ReaderSync, Writer, WriterSync {
#buf: Uint8Array; // contents are the bytes buf[off : len(buf)]
#off = 0; // read at buf[off], write at buf[buf.byteLength]
constructor(ab?: ArrayBuffer) {
if (ab == null) {
this.#buf = new Uint8Array(0);
return;
}
this.#buf = new Uint8Array(ab);
}
bytes(): Uint8Array {
return this.#buf.subarray(this.#off);
}
empty(): boolean {
return this.#buf.byteLength <= this.#off;
}
get length(): number {
return this.#buf.byteLength - this.#off;
}
get capacity(): number {
return this.#buf.buffer.byteLength;
}
truncate(n: number): void {
if (n === 0) {
this.reset();
return;
}
if (n < 0 || n > this.length) {
throw Error("bytes.Buffer: truncation out of range");
}
this.#reslice(this.#off + n);
}
reset(): void {
this.#reslice(0);
this.#off = 0;
}
#tryGrowByReslice = (n: number): number => {
const l = this.#buf.byteLength;
if (n <= this.capacity - l) {
this.#reslice(l + n);
return l;
}
return -1;
};
#reslice = (len: number): void => {
assert(len <= this.#buf.buffer.byteLength);
this.#buf = new Uint8Array(this.#buf.buffer, 0, len);
};
readSync(p: Uint8Array): number | null {
if (this.empty()) {
// Buffer is empty, reset to recover space.
this.reset();
if (p.byteLength === 0) {
// this edge case is tested in 'bufferReadEmptyAtEOF' test
return 0;
}
return null;
}
const nread = copyBytes(this.#buf.subarray(this.#off), p);
this.#off += nread;
return nread;
}
read(p: Uint8Array): Promise<number | null> {
const rr = this.readSync(p);
return Promise.resolve(rr);
}
writeSync(p: Uint8Array): number {
const m = this.#grow(p.byteLength);
return copyBytes(p, this.#buf, m);
}
write(p: Uint8Array): Promise<number> {
const n = this.writeSync(p);
return Promise.resolve(n);
}
#grow = (n: number): number => {
const m = this.length;
// If buffer is empty, reset to recover space.
if (m === 0 && this.#off !== 0) {
this.reset();
}
// Fast: Try to grow by means of a reslice.
const i = this.#tryGrowByReslice(n);
if (i >= 0) {
return i;
}
const c = this.capacity;
if (n <= Math.floor(c / 2) - m) {
// We can slide things down instead of allocating a new
// ArrayBuffer. We only need m+n <= c to slide, but
// we instead let capacity get twice as large so we
// don't spend all our time copying.
copyBytes(this.#buf.subarray(this.#off), this.#buf);
} else if (c > MAX_SIZE - c - n) {
throw new Error("The buffer cannot be grown beyond the maximum size.");
} else {
// Not enough space anywhere, we need to allocate.
const buf = new Uint8Array(2 * c + n);
copyBytes(this.#buf.subarray(this.#off), buf);
this.#buf = buf;
}
// Restore this.#off and len(this.#buf).
this.#off = 0;
this.#reslice(m + n);
return m;
};
grow(n: number): void {
if (n < 0) {
throw Error("Buffer.grow: negative count");
}
const m = this.#grow(n);
this.#reslice(m);
}
async readFrom(r: Reader): Promise<number> {
let n = 0;
while (true) {
const i = this.#grow(MIN_READ);
this.#reslice(i);
const fub = new Uint8Array(this.#buf.buffer, i);
const nread = await r.read(fub);
if (nread === null) {
return n;
}
this.#reslice(i + nread);
n += nread;
}
}
readFromSync(r: ReaderSync): number {
let n = 0;
while (true) {
const i = this.#grow(MIN_READ);
this.#reslice(i);
const fub = new Uint8Array(this.#buf.buffer, i);
const nread = r.readSync(fub);
if (nread === null) {
return n;
}
this.#reslice(i + nread);
n += nread;
}
}
}
export async function readAll(r: Reader): Promise<Uint8Array> {
const buf = new Buffer();
await buf.readFrom(r);
return buf.bytes();
}
export function readAllSync(r: ReaderSync): Uint8Array {
const buf = new Buffer();
buf.readFromSync(r);
return buf.bytes();
}
export async function writeAll(w: Writer, arr: Uint8Array): Promise<void> {
let nwritten = 0;
while (nwritten < arr.length) {
nwritten += await w.write(arr.subarray(nwritten));
}
}
export function writeAllSync(w: WriterSync, arr: Uint8Array): void {
let nwritten = 0;
while (nwritten < arr.length) {
nwritten += w.writeSync(arr.subarray(nwritten));
}
}